This is my Uncle George (Yuriy/Yurko) Melnykovych, the son of my grandfather's sister. According to my Aunt Marijka, the picture is probably from the early 1940s, 1943 or earlier, though it had been identified as 1948 in pencil on the back. He is wearing a Ukrainian Scout uniform. His mother was Maria and his father Olexander; they both died of tuberculosis. Yurko and his sister Marta were only eight and four, respectively; my grandfather raised them. He became a microbiologist (I think) and specialized in cancer research, with the University of Kansas. Sadly, I never got to know him or his family, though I know my Mom spoke with him at times. I once tried to visit them when I took a trip out west, but it didn't come to pass. I seem to recall that my Dad talked with him after my mother died, and explained the rare cancer that felled her.
Not one hundred percent sure, but this looks like George as well, in a picture taken in 1949.